Privacy

Cylin makes practice apps for children: Vocabulary, Multiplication and Piano Sight Reading, and Cylin Hub, where parents manage the family. This page explains what information we collect, why, and the choices you have. It applies to cylin.app, Cylin Hub and all three apps.

Last updated: October 9, 2026

Who we are

The Cylin apps are made and run by Cylin (“we”, “us”). You can reach us at support@cylin.app about anything on this page, including your family’s information.

The short version

A parent creates the account. Children never need an email address or a password.
We collect what the apps need to work and to show you your child’s progress, and nothing else.
No advertising, no third-party analytics or tracking, and we never sell information.
You can see your children’s progress in Cylin Hub, remove a child at any time, and delete your account and everything in it.

What we collect

From you, the parent

Your email address and a password, to create and secure your account. Passwords are handled by our sign-in provider and stored only in hashed form.
A family name you choose, and a parent PIN that keeps grown-ups areas closed to children. We store the PIN only in hashed form.
Settings you choose for each child, such as a starting grade, interests, daily practice time, and word lists you create in Vocabulary.

About your children

A first name or nickname and an avatar colour, which you enter in Cylin Hub. Please use a nickname if you prefer.
Learning progress in each app, so it follows your child between devices and shows in Cylin Hub. In Vocabulary this includes whether each answer was right, how long it took and whether a hint was used, and an estimate of your child’s vocabulary level. We do not store the text a child types.
Practice time: when a session started and ended, and a few totals such as questions answered, so you can see your child’s week in Cylin Hub.
In Piano Sight Reading, the name and colours a child picks for their adventurer.
Simple records of what happened in an app, such as a lesson started or a word introduced. They contain no free text. We use them to fix problems and improve the apps.

Automatically

Like every website, our hosting provider receives your device’s IP address and browser details when pages load, and keeps short-lived logs for security and reliability.
A sign-in cookie that keeps you signed in across Cylin Hub and the apps, and information stored on your device so the apps work offline and remember settings. We use no advertising or analytics cookies.

What we never collect

Audio. Piano Sight Reading uses your microphone only to hear which note is played, and the sound is processed on your device. It is never recorded or sent to us.
Photos, location, contacts, or a child’s email address or phone number.

What stays on your device

Every Cylin app needs a parent’s Cylin account. Each app also keeps a copy of your children’s progress and settings on the device, so it works offline and starts quickly. Progress from before an app was linked to Cylin Hub stays on that device until you add the child in Cylin Hub with the same name. Progress files you choose to save are stored wherever you save them.

How we use it

To run the apps: sign you in, choose the next words, facts or levels for each child, and keep progress in step across devices.
To show you, the parent, how each child is getting on in Cylin Hub.
To send account emails you ask for, such as confirming your email or resetting your password. We send no marketing email.
To keep the service secure, fix problems and improve the apps.

We do not use children’s information for advertising, and we do not build profiles of children for any purpose other than their learning in the apps.

We never sell or rent information. We share it only with service providers who run parts of Cylin for us and may use it only for that:

Supabase, which hosts our database and handles sign-in and account emails.
Vercel, which hosts our websites and apps.

If you invite another parent or guardian into your family in Cylin Hub, they see and manage your children’s names, progress and practice time, as you do. You can remove a parent you invited at any time.

We may also disclose information if the law requires it, or to protect the safety of a child or the security of the service. If Cylin is ever transferred to a new owner, this policy will continue to protect the information collected under it, and we will tell you first.

Children’s privacy

Cylin is made for children, under the direction of a parent or guardian. Only an adult can create an account, and a child can use the account-based apps only after their parent adds them in Cylin Hub. Creating the account and adding your child is your consent to the collection described here. We collect only what a child needs to use the apps, and a child never has to give more to keep playing.

As a parent you can at any time:

See your child’s progress and practice time in Cylin Hub.
Change or correct your child’s name and settings.
Remove your child in Cylin Hub. Their name, progress, practice time and app records are deleted from our database straight away.
Delete your whole account in Cylin Hub, under Settings → Delete account. Your family, children, their progress and practice time, and your PIN are deleted at once.
Ask us to stop collecting your child’s information, or to delete your account for you, by emailing support@cylin.app from your account’s email address.

How long we keep it

We keep your family’s information while your account is open. When you remove a child, their information is deleted at once. When you delete your account in Cylin Hub, it is deleted at once; if you ask us by email instead, we delete it within 30 days. Copies in our provider’s backups are overwritten on their regular schedule after that.

Security

Connections to Cylin are encrypted. Each family’s information is separated in the database so that one family can never see another’s, and grown-ups areas are protected by your parent PIN. No system is perfectly secure, so please choose a strong password and tell us at once if you think your account has been misused.

Changes

If we change this policy, we will update the date at the top. If a change affects how we use your children’s information, we will email you before it takes effect and ask for your consent where the law requires it.

Questions and requests

Email support@cylin.app. We aim to reply within a few days.